Process for preparing 2-chloro-4-nitrophenol



Patented Feb. 24, 1953 PROCESS FOR PREPARING 2-CHLORO-4- NITROPHENOL Everett E. Gilbert, :F lushing, and Jack TV. Schurman, Bellaire, N. 56., assignors to Allied-Chemical & Dye Corporation, New ,York, N. Y., acorporation of New York No Drawing. Application April 23, 1951,

.Serial' No. 222,520

.6 Claims. 1 This invention :relates :to an improved process for preparing 12-,chloro-,4-:nitropheno1 :utilizable as a bactericide and/or fungicide- ,It :has been proposed :to :produce 'izgchloroinitrophenol by caustic hydrolysis of .lfi-Ili I 13,f

dichlorobenzene. This processghowever, :is subject to itheimportant disadvanta e that the raw material "is .difiilcult to prepare pure, requiring laborious "separation with consequent reduetien in yield. Further proposals have been made to produce 12-ch1oro-4,nitrophenol by "chlorination .of 4-,nitrol1henoL- but, to ;,our knowledge, none has :resulted in aicommercially v practicable process.

.Itis an objectof thisinvention to provide an improved process for the productionof 2-chloro- .A-nitrophenol by chlorination of ,i-nitroph no Another object of the invention is to recover as a by-product of such process, substantiallypure aqueous hydrochloric acid solution. Other objects andadvantages-of the invention will appear hereinafter.

In accordance with the invention, -chloro-4- .nitrophenol is manufactured "by reacting i-nitrophenol with: chlorine in the-presenceof an aque- I aqueousFHCl-solution g "No: NO:

On completion of the chlorination reaction,

and after cooling,if necessary'the reaction prodnot appears .as a crystalline slurry and'is'filtered to remove the desired 2-chloro-4-nitrophenol as acrystalline solid. After washing the 2-chloroi nitrophenol with water "to extract any watersoluble compounds present, theproduct is "then dried to constant weight and is ready for immediate use, without further treatment, as or in bactericidal or fungicidal preparations.

The present reaction may be carried out conveniently in a reactor provided with means for heating and cooling the contents of the reactor and equipped with a high speed stirrer, inlet tubes for charging gas, liquid and solid and a reflux condenser leading to a suitable scrubbing system.

Generally, any temperature at which the 4- nitrophenol is molten may be employed in the process of the invention. However, since temperatures below 70 C. are often incapable of 2 maintaining the :4-nitrophenol in ,molten con.- ditionand those above 90C. tend to favor .decompositionreactions, we prefer to use temperatures within the range of about to;9 0 C.

Time of reaction may vary greatly, say from about 1 to 10 hours, depending principally ,upon the particular temperature employed.

We have found that 2-chloro-4-nitrophenol crystallizes ,ata higher temperature from strongeraqueous hydrochloric acid solutions than from weaker aqueous hydrochloric acid solutions ,or water. This discovery ,makes possible the preparation of .a purer v2-chloro-i nitrophenol prod.- .uct vsinceby employing the stronger aqueous hy- .drochloric acid solutions, crystallization of the product may be efiected al higher temperatures at which unconverted starting material v(and possibly by-products) have greater solubility the aqueous phase. Accordingly, in the process of our invention, we prefer to employ aqueous hydrochloric acid solutions rangin in strength from vabout 2.0.0 to 35.0% by weight. Th amount of aqueous hydrochloric acid solution used ispreferably about 2 to 15 times that of the i-nitrophenol-employed, such amount resulting in the formation of a suspension of the A-nitrophenol. Greater amounts of hydrochloric acid solution mayibeemployed but are unnecessary and are usually undesirable since they have the disadvantage of increasing the volume .of reaction mixture to be handled.

As may be seen from the above equationjllustrating the reaction of :the invention, ;1 mol of which is saturated at the temperature of reac.-- tion, hydrogen chloride byproduct distilled .out as vapors and maybe-conveniently collected -;in a water trap as substantially pure aqueous hydrochloric acid solution.

As is obvious to those skilled in the art, the process of the present invention is applicable to a recycle type operation in which the filtrate obtained when the 2-chloro-4-nitrophenol is isolated is charged with fresh i-nitrophenol for the next run and constitutes a substantial part of the aqueous hydrochloric acid solution required therefor.

If required or desired, the Z-chloro--nitrophenol product produced by this invention may be converted into its sodium salt. This is accomplished, for example, by direct neutralization of a water slurry of the product with a caustic soda solution. The resulting neutral slurry can 3 then be spray or drum dried and marketed with some sodium chloride content or the product filtered off and the mother liquor used for the next run.

The following examples describe ways in which the principle of the invention has been applied but is not to be construed as limiting the invention. Parts are by weight.

Example 1 235 parts of 36% aqueous hydrochloric acid solution, 89.8 parts of water and 60.0 parts of 4- nitrophenol were heated together in a reactor at 80 C. with vigorous stirring to produce an emulsion. 30.9 parts of chlorine were then added over the course of 2 hours at 80 to 85 C. Heating was continued with stirring for 30 minutes during which period the oily product crystallized. No hydrogen chloride was distilled out during the chlorination. The crystalline product was filtered, washed with water and air dried at room temperature to constant weight. The resulting product, having a pink appearance, was good quality 2-chloro-4-nitrophenol and constituted 70.5 parts (94.1% yield based on the 4-nitrophenol) melting at 101 to 109 C.

Example 2 27.0 parts of 4-nitrophenol were suspended in a mixture of 235 parts of 36% aqueous hydrochloric acid solution and 34.4 parts of water and the resulting mixture heated in a reactor at 65 C. with vigorous stirring. 13.5 parts of chlorine were then admitted over a period of 3 hours, the final temperature rising to 85 C. 7.5 parts of hydrogen chloride were collected in a water trap to form a substantially pure aqueous hydrochloric acid solution, Heating and stirring were then continued for 1% hours. On cooling slightly, the reaction product crystallized. Upon filtration, washing and drying to constant weight at room temperature, 29.8 parts (88.4% yield based on the 4-nitrophenol) of good quality 2-chloro- 4-nitrophenol, having a cream color and melting at 104 to 110 C., were obtained.

Although certain preferred embodiments of the invention have been disclosed for purpose of illustration, it will be evident that various changes and modifications may be made therein without departing from the scope and spirit of the invention.

We claim:

1. A process for preparing 2-chloro-4-nitrophenol which comprises reacting 4-nitrophenol with chlorine in the presence of an aqueous hydrochloric acid solution at a temperature at which the l-nitrophenol is molten but below a temperature at which substantial decomposition occurs, and recovering the 2-chloro-4-nitrophen01 formed from the aqueous hydrochloric acid solution.

2 A process for preparing 2-chloro-4-nltrophenol which comprises reacting i-nitrophenol with chlorine in the presence of an aqueous hydrochloric acid solution ranging in strength from about 20.0 to 35.0% by weight at a temperature at which the l-nitrophenol is molten but below a temperature at which substantial decomposition occurs, and recovering the 2-ch1oro-4-nitrophenol formed from the aqueous hydrochloric acid solution.

3. A process for preparing 2-chloro-4-nitrophenol which comprises reacting 4-nitrophenol with chlorine in the presence of an aqueous hydrochloric acid solution ranging in strength from about 20.0 to 35.0% by weight at about to C., and recovering the 2-chloro-4-nitrophenol formed from the aqueous hydrochloric acid solution.

4. A process fOr preparing 2-chloro-4-nitrophenol which comprises reacting 4-nitrophenol with chlorine in the presence of an aqueous hydrochloric acid solution ranging in strength from about 20.0 to 35.0% by weight at about 70 to 90 C., the quantity of hydrochloric acid solution being about 2 to 15 times that of the 4-nitrophenol, and recovering the 2-chloro-4-nitrophenol formed from the hydrochloric acid solution.

5. A process for preparing 2-chloro-4-nitrophenol which comprises reacting 4-nitrophenol with chlorine in the presence of an aqueous hydrochloric acid solution at a temperature at which the e-nitrophenol is molten but below a temperature at which substantial decomposition occurs, the hydrochloric acid solution being saturated at the temperature of reaction, recovering vapors of hydrogen chloride formed as by-product, and recovering the 2-chloro-4-nitrophenol formed from the aqueous hydrochloric acid solution.

6. A process for preparing 2-chloro-4-nitrophenol which comprises reacting 4-nitropheno1 with chlorine in the presence of an aqueous hydrochloric acid solution at a temperature at which the l-nitrophenol is molten but below a temperature at which substantial decomposition occurs, the hydrochloric acid solution being saturated at the temperature of reaction, recovering vapors of hydrogen chloride formed as by-prodnot by contacting them with water, and recovering the 2-chloro-4-nitrophenol formed from the aqueous hydrochloric acid solution.

EVERETT E. GILBERT. JACK V. SCHURMAN.

REFERENCES CITED The following references are of record in the file of this patent:

Bogdanov et al., Chem. Abstracts, vol. 39 (1945) col. 948 (1 page only). 

1. A PROCESS FOR PREPARING 2-CHLORO-4-NITROPHENOL WHICH COMPRISES REACTING 4-NITROPHENOL WITH CHLORINE IN THE PRESENCE OF AN AQUEOUS HYDROCHLORIC ACID SOLUTION AT A TEMPERATURE AT WHICH THE 4-NITROPHENOL IS MOLTEN BUT BELOW A TEMPERATURE AT WHICH SUBSTANTIAL SECOMPOSITION OCCURS, AND RECOVERING THE 2-CHLORO-4-NITROPHENOL FORMED FROM THE AQUEOUS HYDROCHLORIC ACID SOLUTION. 